The living cell, the smallest unit of living organism, has been studied to a very great extent. The morphological development of cells as well as, to a lesser degree, the essentials of the importance and functioning of the various subcellular structures are thoroughly understood. The cell membrane has also been the subject of exhaustive studies. As a result, subjects such as active and passive transport, inhibited or facilitated diffusion, countercurrent effects, pump effects, excitatory processes and the evalution impulses are all fairly well understood. It is thus very surprising that interfacial properties of membranes have been paid so little attention, although it is easy to see that many, if not the majority of membrane functions, are strongly influenced by membrane interfacial activity. The idea, that changing the interfacial activity might play a central role in central regulation and influencing mechanisms, is not so far-fetched, bearing in mind that changes in the activity of interfaces not only influence membrane permeability, but also the electrical potential thresholds which occur there. The fact that a desired activity may be brought about by influencing the activity of membrane interfaces is suggested by the following two factors: Firstly, the permeability of the membrane determines the direction amount and type of material to be transported through a membrane. Secondly, the membrane potential plays an important role in the transmission of impulses, a function that is regulated by changes in permeability.
However, influencing the interfacial activity by means of surfactant is frowned upon by most experts, as the surfactants are generally thought of as being highly toxic substances. This type of substance lowers the interfacial activity of the membrane to such an extent that its disruption is caused, at concentrations far lower than necessary for biological or pharmadynamic effects. Thus, surfactants are generally cytolytic in that they disrupt the membrane and destroy the cell. This cytolytic activity rises with increased surfactant absorption, in its accumulation in the membrane. Similarly, slow rates of metabolism also increase surfactant activity.
Lysolecithins, which are acyl-glyceral phosphorylcholine esters, are interfacially activity and are known to be cytolytic at high concentrations. In spite of this, the lethal dose of lysolecithins is relatively high, due to the fact that they are extremely rapidly metabolized by reacylation to lecithin or deacylation to glycerylphosphorylcholine.